928vette

Installed 2001 vette LS1 into Porsche 928 in July, the car started on first try. I then disabled VATS and the car has been running very well ever since. Just made round trip Vegas/Los Angeles. Then, two days ago, the car would not start properly.

SYMPTOMS:
- Car starts/runs perfectly for 2 seconds then abruptly shuts down, accelerator and engine works properly during the 2 secs. Because the shutdown is abrupt and is precisely the same duration each time, it appears to me that the shutdown is performed by the PCM.

TESTS THUS FAR:
- Have perfect 58 psi on fuel rail before, during, and after each start.
- Runs perfectly for the 2 seconds, no misses, smooth as always.
- Pulled the power to the PCM several times.
- Charged the battery full. Using a multimeter, when I start the car I see 12.4V before, the voltage dips to 10V while starter is engaged, then goes to 14V as the alternator starts working.
- Curiously, the PCM reports about .8 volts lower battery voltage than my multimeter.
- Checked grounds. Large strap from engine to chassis. Two ground wires from the PCM are grounded to chassis.
- Fuel tank was removed and cleaned and two new fuel filters (one Porsche, one Chevy) were installed in July. I added 5 fresh gallons of fuel to the tank.
- I turned off VATS back in July, no reason it would just re-enable itself. I read the calibration from the computer and it shows that VATS is off. I also scanned the VATS bit and it shows 'passed'.
- HPTUNERS always loses sync when I start the engine, this has always been the case so I assume it is normal, but the point is that I cannot acquire a log of all of the engine parameters during the 2 seconds. After the 2 second run, I receive the following DTC's:

[PCM] P0102 - Mass Air Flow (MAF) Sensor Circuit Low Frequency (Pending) (Old) (Current) (Immature)
No problem, I pulled the MAF connector (to eliminate MAF as the cause) because I know the engine runs fine without it.
[PCM] P0412 - Secondary Air Injection (AIR) Solenoid Relay Control Circuit Bank 1 (Pending) (Old) (Current) (Immature)
AIR is not yet connected, this DTC has always been here.
[PCM] P0449 - Evaporative Emission (EVAP) Vent Solenoid Control Circuit (Pending) (Old) (Current) (Immature)
Not yet connected, this DTC has always been here.
[PCM] P0522 - Engine Oil Pressure Sensor/Switch Circuit Low Voltage (SES) (Pending) (Old) (History) (Current) (Immature)
I installed an oil pressure sensor that sends to the Porsche instrument panel back in July. This DTC has always been here.
[PCM] P0645 - Air Conditioning (A/C) Clutch Relay Control Circuit (Pending) (Old) (History) (Current) (Immature)
Should not cause engine not to start, this DTC has always been here.
[PCM] P0654 - Engine RPM Output Circuit Malfunction (Pending) (Old) (History) (Current) (Immature)
My understanding is that this is the circuit between the PCM and the vette instrument panel. I do not have the RPM connected to a tach, this DTC has always been here.
[PCM] P0803 - 1-4 Upshift (Skip Shift) Solenoid Control Circuit Malfunction (Pending) (Old) (Current) (Immature)
Would this cause the PCM to shut down?
[PCM] P0804 - 1-4 Upshift (Skip Shift) Lamp Control Circuit Malfunction (Pending) (Old) (History) (Current) (Immature)
Would this cause the PCM to shut down?
[PCM] P1336 - Crankshaft Position (CKP) System Variation Not Learned (SES) (Pending) (Old) (History) (Current) (Immature)
I broke the original PCM (don't ask) so the current one is a replacement, thus the CKP is not calibrated. In my research, it appears that this does not normally cause the engine to shut down, in fact, the engine has to reach operating temperature before you can perform the CASE read in order to clear it. On the other hand, could this be identifying a CKP problem? I would think the PCM would produce a different DTC if it were having a real problem with the CKP.

SUMMARY
The real question is: What can cause the PCM to shutdown in 2 seconds that would not produce a useful DTC. There were a lot of DTC's turned off when I received this replacement PCM, is it possible that the DTC that would display the cause of this problem is disabled? Is there a comprehensive list of specific things that can cause the PCM to decide to shutdown the engine?
Could the battery voltage dipping during start causes the PCM to shutdown? The system acts EXACTLY as it did when VATS was turned on so I will try enabling it and then re-disabling it.

I'm stumped on this one, I didn't have this much trouble making it work in the first place. I've done my best to test and document as much as possible so I don't waste anyone's time, any help or suggestions would be very much appreciated.

Thanks to any and all

Tongboy

Sounds exactly like vats to me.I fought it being vats the first time with a bypass I'm place but our totally was.hp tuners shouldn't disconnect on crank assuming you have the wiring plumbed correctly to the ecu.I would make sure route ecu 12v constant is wired correctly as well as your 12v to your ecu while cranking is staying hot.solving that issue should let you troubleshoot the bigger issue more easily.

importhater81

Issues with the steering column lock relay will cause the exact symptoms your having.There was even a recall for this problem.

vidal77boxing

iTrader: (15)

car has a fuel cut off feature. It shuts off after 2mph. You can have the feature deleted using a tuning program. Run a search on fuel cutoff. I had same issue when having probs on my c5 due to a column lock malfunction. VERY ANNOYING.

Corvetteforum is a good source of information. Good luck

COSTIGAN86

iTrader: (8)

Does it shut off after 2 seconds while idling? Or will it idle until you move it then die? If it is a column lock issue, it will idle but the PCM shuts off fuel after 1 or 2 mph.

928vette

From my reading, it appears that the column lock kills the fuel after the car reaches 2mph or more, I don't know if that means it kills the fuel pump or the injectors, but this is probably not the problem because:
1) There is no speed information going into the engine. It has run that way since July, so shouldn't be a problem. As far as the engine knows, it is simply being revved but the car is not moving. It doesn't produce a DTC complaining about speed, so it doesn't appear to know that it is not connected.
2) The column lock information goes to the BCM which communicates to the PCM. I do not have a BCM in the car.

I am not ruling this out, perhaps the problem could be related to having no BCM or no speed input, but why it would work until now is still a mystery.

No troubleshooting today; had to retrieve the car. It was about 3 miles away - uphill (fortunately). Ran for 3 seconds at a time across the hill, then coasted down. Pretty silly, but at least she's home.

zamora7

iTrader: (4)

What about the oil pressure sensor. I remember reading that on a LS engine(can't remember which) once the oil pressure dropped below a certain psi it would shut down. But it can also be a bad pcm, not sure if it would cause this.

busta9876

iTrader: (3)

I had a 02 Corvette M6 program I did for a swap, that would not restart hot. I was able to reproduce the same complaint in my vehicle (89 caprice 5.3 drive by wire) I programmed pcm again, this time I unchecked Column Lock option I had missed the first time, and put Column Lock Fuel Cutoff Disable to 255 mph. All was good then.

I can not explain, but for whatever reason, it would shut it off when warm. It would start from COLD and run as long as you wanted, but once it got over about 150 or so, no restart.

Just my experience...

Droptoplt1ta

Unplug or swap MAF to see if concern is still present

5.3LJimmy

iTrader: (10)

You say you are using a different PCM than the original from the swap, but you aren't clear on when you installed the new one. Is this a problem that has started with the new PCM or has the car ran normally with it?

928vette

The new PCM was installed back in July, so the car ran fine with this computer for several months.